The importance of maintaining an effective air and vapor barrier within the exterior walls of a building, particularly in colder climates where the outside environment's temperature and relative humidity levels are typically much lower than those desired on the inside of the building, has long been appreciated. It has been found, for example, that the exterior walls of older buildings, typically consisting of a frame with only wall panel material such as plaster or sheetrock on the interior side thereof, and conventional siding or bricking material on the exterior, even with insulation therebetween, generally provide a relatively poor barrier to the exchange of air and vapor between the outside and inside of the building.
In an effort to minimize such air and vapor exchange, over the past several years much of the new construction incorporates a thin sheet of plastic material, commonly referred to as "air and vapor barrier", disposed between the interior wall panel and underlying frame of a building's exterior walls. Also, as the energy costs required for heating buildings have increased over recent years, new construction continues to include more energy efficient doors and windows and improved types of insulation.
Despite the use of such improved building materials, however, it is found that a substantial amount of cold air continues to enter the building, and heated air and humidity escapes therefrom, through the various openings cut in the interior wall panel and underlying air and vapor barrier of the building's exterior walls at those locations where electrical outlet boxes, containing electrical switches or plug-ins, are mounted. Part of the air and vapor leakage typically occurs through the electrical outlet unit itself, primarily through the various wire access holes which are provided in the sides of the electrical outlet box for insertion of electrical wiring to be connected to electrical apparatus mounted therein, and part of the air and vapor leakage also occurs around the outside of the electrical outlet box due to the fact that there is typically no seal between the air and vapor barrier opening and the electrical outlet box inserted therethrough.
Electrical outlet boxes are typically installed in alignment with an opening in a wall panel, with the box fastened to a stud or other structural member of the building's frame. When such electrical outlet boxes are installed on exterior walls, an aligned opening approximately the size of the forward opening of the electrical outlet box is cut in the air and vapor barrier and interior wall panel. Since there has not heretofore been a means available for providing a seal between the outside periphery of such an electrical outlet box and the air and vapor barrier and interior wall panel through which such box is mounted, a substantial leakage of air and vapor occurs. Furthermore, since a building typically has several such electrical outlet units distributed throughout several locations of its exterior walls, the cumulative loss of heat and humidity during a given period of cold weather can be significant, resulting in much higher energy costs for heating and making the environment within such a building generally uncomfortable.
Thus, there is a need for an improved electrical outlet unit for installation in a building's exterior wall, which will provide a seal around the periphery of said unit with the air and vapor barrier in said wall, as well as a seal around the electrical wires which pass through the wire access openings of said unit, so as to minimize the exchange of air and vapor between the inside and outside of such building's exterior wall.